Stanford University's Hopkins Marine Station, Pacific Grove, CA

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Squid in Swimsuits – Tracking Humboldt Squid off the California Coast

The Secret Lives of Squid. Professor William Gilly releases a Humboldt squid with a pop-up satellite tag on a research trip off California. Professor Gilly’s lab uses tag data and footage from video cameras attached to Humboldt squid to understand the species’ movements and behaviors, including squid group dynamics. (Image from Captain Dave Murline, R/V New Horizon; Courtesy of Professor William Gilly)

Squid have long been portrayed in books and myths as the infamous adversary of mariners – mysterious creatures who only emerge from the ocean depths to harass hapless sailors. But Stanford Professor William Gilly of the Hopkins Marine Station has set out to track and understand the real-life movements of a squid species that has started to appear more frequently off the California coast. Dosidicus gigas, known as the Humboldt squid, and 5 feet long in a good year, made headlines last December because of its massive strandings around Monterey Bay. But Gilly believes that this behavior may simply be part of a larger trend in the species’ expansion into temperate waters.

Gilly’s lab has begun to attach satellite pop-up tags and video cameras to Humboldt squid, which is quite a feat considering that a squid’s body is designed to be as slippery, streamlined and flexible as possible to glide through the water. The research team had to invent a method which involved slipping a child’s bathing suit around the squid’s body, and attaching tags or cameras to that, but it’s been worth the hassle. Video footage directly from a squid’s view gives Gilly’s lab unique perspective on social behaviors from “inside the pack”, and offers glimpses of the secrets of their lives. Squid have been seen meeting in large congregations and remaining in a certain area for several hours – whether to mate, hunt or socialize for other reasons, researchers don’t yet know.

Bathing Beauty — Researchers from the Gilly lab at Hopkins quickly strap a satellite pop-up tag onto a Humboldt squid off the California coast, before releasing it to track its vertical and geographic movements. Gilly’s lab has invented ways to attach tags to the smooth, slippery bodies of squid using a modified child’s bathing suit. (Image from Captain Dave Murline, R/V New Horizon; Courtesy of Professor William Gilly).

Tagging data also reveals that the Humboldt squid may be able to swim and feed in low-oxygen layers in the ocean, where most fish cannot. Squid are known for their propulsive water jets, which help them burst upward, then gently glide down, tracing vertical zigzags to conserve energy instead of swimming constantly. But in low-oxygen waters, they appear to lose their quick speed bursts. To test squid oxygen limits, Gilly’s lab created the equivalent of a human treadmill, where they place squid in tanks and stimulate them to swim rapidly, mimicking the speed of their jet bursts. The researchers then decrease oxygen levels and test whether squid maintain their fast movements. Gilly has found that at low oxygen levels, squid simply cannot keep swimming fast, and begin to show a body stress response. So as low-oxygen layers expand with increasing ocean temperatures, Humboldt squid will probably be able to expand their habitat ranges and continue to capitalize on prey availability – but they won’t always be able to perform at their highest level.

And the squid strandings of last winter? In contrast to the media hype, Gilly believes it’s a typical behavior when squid move into a new area. They are simply “testing the waters”, some of which – like sandy beaches above the surfline – don’t work out to colonize. As waters warm and low-oxygen areas expand northward along the California Current, though, the Humboldt squid may be here to stay as the newest, and most successful, marine predator off our coast.